Converting px to ems with LESS

gistfile1.css

/* Create variables [optional] */
@basefont: 14; // in pixels
@baseline: 20; // in pixels
 
/* Create a converter namespace [optional] */
#pxtoem {
  /* Create convert mixin [required] */
  .font-size( @target: @basefont, @context: @basefont ) {
    font-size: (@target / @context) + 0em;
  }
}


/* Example */
a {
  #pxtoem > .font-size( 10, 14 );
}

Source: http://www.ifdattic.com/2011/10/19/converting-px-to-ems-with-less/